This invention relates to vehicles convertible from highway to railroad mode of travel and vice versa, and in particular, to the coupler apparatus employed to join adjacent vehicles together to form a train for the railroad mode.
The utilization of a single vehicle that may be convertible from highway to railroad mode of travel has distinct advantages that may be readily recognized. For example, when the vehicle is transferred from one mode of operation to another, since the same vehicle will be employed, it is not necessary to off-load any cargo from, for example, a railroad vehicle to a highway vehicle or vice versa. By utilizing the same vehicle for both highway and railroad modes of travel, significant savings in time and labor may be obtained.
In the railroad mode of operation, adjacent vehicles are coupled end-to-end to form a train. As is the case with standard railroad car couplers, the coupling device used on the dual mode vehicles must accommodate limited rolling, pitching and relative vertical displacement between coupled vehicles. Heretofore, it has been suggested that a spherical bushing diposed in a vertically extending hole of the male member of the coupling device, in combination with a spherical seat, will provide suitable means for accommodating the limited relative motion between adjacent vehicles. The foregoing design results in metal-to-metal contact between the spherical bushing and the spherical seat. Under conditions when rust or other foreign matter accumulate on the seat, the required articulation of the spherical bushing and associated male coupling member may be made quite difficult whereby high stresses may be produced in the coupling male member. Further, this design is expensive as it requires a significant amount of machinery.
Accordingly, it is an object of the invention to couple adjacent vehicles of a convertible rail-highway semi-trailer operating in the railroad mode with relatively inexpensive coupling means that can accommodate limited rolling, pitching and relative vertical displacement between coupled vehicles.